1. Field of the Invention
The present invention relates to a composite valve which is preferably used in a heat pump type cooling and heating system or the like, and more particularly to a composite valve which is provided with a pilot type large flow rate control valve and a small flow rate control valve.
2. Description of the Conventional Art
As a heat pump type cooling and heating system, there has been conventionally known a structure which is provided with a compressor, a condenser, an evaporator, an expansion valve and a four-way valve for inverting a refrigerant flow path.
On the other hand, as a heat pump type cooling and heating system for a vehicle (for example, for an electric vehicle), there has been proposed a system which does not invert a flow of a refrigerant and is provided independently with an expansion valve for cooling and an expansion valve for heating, for example, as shown in FIG. 1 of Japanese Official Gazette of Patent No. 3799732.
The flow of the refrigerant is not inverted in the system mentioned above. Accordingly, for example, paying attention to an expansion valve for heating (reference numeral 24 in the document) shown in FIG. 1 of the document, there is provided such a system that an electromagnetic valve for cooling (reference numeral 26 in the document) is provided in parallel in the expansion valve for heating, a heating operation is carried out by closing the electromagnetic valve for cooling and narrowing down the refrigerant by means of the expansion valve for heating at a time of heating, and the expansion valve does not carry out the narrowing down of the refrigerant by setting the electromagnetic valve for cooling open and bypassing the inlet and outlet of the expansion valve for heating at a time of cooling.
In the meantime, if the expansion valve and the electromagnetic valve for bypassing are respectively provided, the system is enlarged in size, and there is a risk that an electric power consumption is enlarged.
Accordingly, it is thought to achieve these functions by one electrically operated valve. In other words, for example, the refrigerant may be narrowed down by the electrically operated valve at a time of heating, and the electrically operated valve may be fully opened at a time of cooling.
In this case, a description will be given of one example of a conventional electrically operated valve with reference to FIG. 8.
An electrically operated valve 1′ in an illustrated example is provided with a valve shaft 25 which has a lower large diameter portion 25a and an upper small diameter portion 25b, a valve main body 40 which has a valve chamber 41, a can 60 which is bonded in a sealing manner to the valve main body 40 in its lower end portion, a rotor 30 which is arranged in an inner periphery of the can 60 so as to be spaced at a predetermined gap a, and a stator 50A which is outward fitted to the can 60 so as to rotationally drive the rotor 30.
The valve shaft 25 is integrally provided with a valve body portion 44 having a specific shape (two stages of inverted circular truncated cone shapes respectively having predetermined angles of center) in a lower end portion of the lower large diameter portion 25a, and the present electrically operated valve 1′ is structured such that a passing flow rate of the refrigerant is controlled by changing a lift amount of the valve body portion 44.
The valve chamber 41 of the valve main body 40 is provided in its lower portion with a valve seat 42 with a valve port (an orifice) 43 which the valve body portion 44 comes close to and away from, and is opened in its side portion to a first inlet and outlet 5′, and a lower portion of the valve main body 40 is provided with a second inlet and outlet 6′ so as to be connected to the valve port 43.
The stator 50A is constructed by a yoke 51, a bobbin 52, a stator coil 53, a resin mold cover 56 and the like, a stepping motor 50 is constructed by the rotor 30, the stator 50A and the like, and an elevation driving mechanism for regulating a lift amount (=an opening degree) of the valve body portion 44 with respect to the valve port 43 is constructed by the stepping motor 50, a feed screw (a female thread portion 38 and a male thread portion 48) mentioned below and the like.
A support ring 36 is integrally connected to the rotor 30, and an upper protruding portion of a lower opened and tubular valve shaft holder 32 which is arranged in an outer periphery of a guide bush 46 is fixed, for example, by caulking to the support ring 36, whereby the rotor 30, the support ring 36 and the valve shaft holder 32 are integrally connected.
Further, a lower end portion of the tubular guide bush 46 is pressed into and fixed to a fitting hole 49 provided in an upper portion of the valve main body 40, and (the lower large diameter portion 25a of) the valve shaft 25 is inward inserted slidably to the guide bush 46. Further, in order to move up and down the valve shaft 25 (the valve body portion 44) by utilizing a rotation of the rotor 30, the male thread portion 48 is formed in an outer periphery of the guide bush 46, the female thread portion 38 is formed in an inner periphery of the valve shaft holder 32, and the feed screw is constructed by the male thread portion 48 and the female thread portion 38.
Further, an upper small diameter portion 46b of the guide bush 46 is inward inserted to an upper portion of the valve shaft holder 32, and the upper small diameter portion 25b of the valve shaft 25 is inserted to (a through hole formed in) the center of a ceiling portion of the valve shaft holder 32. A push nut 33 is pressed into and fixed to an upper end portion of the upper small diameter portion 25b of the valve shaft 25.
Further, the valve shaft 25 is outward inserted to the upper small diameter portion 25b of the valve shaft 25, and is normally energized downward (in a valve closing direction) by a valve closing spring 34 constructed by a compression coil spring which is installed in a compression manner between a ceiling portion of the valve shaft holder 32 and an upper end terrace surface of the lower large diameter portion 25a in the valve shaft 25. A restoring spring 35 constructed by a coil spring is provided in an outer periphery of the push nut 33 on the ceiling portion of the valve shaft holder 32, the coil spring being provided for returning in the case that the valve shaft 25 moves in the valve opening direction and an engagement between the female thread portion 38 and the male thread portion 48 is disconnected.
To the guide bush 46, there is firmly fixed a lower stopper body (a fixing stopper) 47 which constructs one of rotation and downward movement stopper mechanisms for inhibiting a further rotation and downward movement at a time when the rotor 30 is rotated and moved downward to a predetermined valve closing position, and to the valve shaft holder 32, there is firmly fixed an upper stopper body (a movable stopper) 37 which constructs another of the stopper mechanisms.
In this case, the valve closing spring 34 is arranged for obtaining a desired seal pressure in a valve closed state in which the valve body portion 44 seats on the valve port 43 (preventing a leakage), and for reducing an impact at a time when the valve body portion 44 comes into contact with the valve port 43.
In the electrically operated valve 1′ structured as mentioned above, the rotor 30 and the valve shaft holder 32 are rotated in one direction with respect to the guide bush 46 which is fixed to the valve main body 40, by supplying an electrifying and exciting pulse to the motor 50 (the stator 50A) in accordance with a first mode, and on the basis of a screw feeding of the thread portions 48 and 38, for example, the valve shaft holder 32 moved downward, the valve body portion 44 is pressed to the valve seat 42, and the valve port 43a is closed.
At a time point when the valve port 43 is closed, the upper stopper body 37 has not come into contact with the lower stopper body 47 yet, and the rotor 30 and the valve shaft holder 32 further rotate and move downward while the valve body portion 44 closes the valve port 43. In this case, since the valve shaft 25 (the valve body portion 44) does not move downward, however, the valve shaft holder 32 moves downward, the valve closing spring 34 is compressed at a predetermined amount. As a result, the valve body portion 44 is strongly pressed to the valve seat 43, the upper stopper body 37 comes into contact with the lower stopper body 47 on the basis of the rotation and the downward movement of the valve shaft holder 32, and the rotation and the downward movement of the valve shaft holder 32 are forcibly stopped even if the pulse supply with respect to the stator 50A is thereafter carried on.
On the other hand, if the electrifying and exciting pulse is supplied in accordance with a second mode to the stator 50A from this fully closed state, the rotor 30 and the valve shaft holder 32 are rotated in a reverse direction to that mentioned above with respect to the guide bush 46 which is fixed to the valve main body 40, and the valve shaft holder 32 moves upward this time on the basis of the screw feeding of the thread portions 48 and 38. In this case, since the valve closing spring 34 is compressed at the predetermined amount as mentioned above, at a time point of starting the rotation and the upward movement of the valve shaft holder 32 (a time point of starting the pulse supply), the valve body portion 44 is not disconnected from the valve seat 42 and remains in the valve closed state (a lift amount=0) until the valve closing spring 34 extends at the predetermined amount mentioned above. Further, if the valve shaft holder 32 is further rotated and moved upward after the valve closing spring 34 extends at the predetermined amount, the valve body portion 44 is disconnected from the valve seat 42 and the valve port 43 is opened, so that the refrigerant passes through the valve port 43.
In this case, it is possible to optionally and finely regulate the lift amount of the valve body portion 44, in other words, an effective opening area (=an opening degree) of the valve port 43 on the basis of an amount of rotation of the rotor 30. Further, since the amount of rotation of the rotor 30 is controlled by a supply pulse number, it is possible to control a flow rate of the refrigerant at a high precision.
Accordingly, in the case that the electrically operated valve 1′ having the structure mentioned above is employed as the electrically operated valve having both functions of the expansion valve and the bypass valve as shown in the Japanese Patent No. 3799732, it is set to a maximum opening degree (a maximum lift amount) in such a manner as to reduce the pressure loss as much as possible so as to achieve the function of the bypass valve, for example, at a time of the cooling operation, and it is set such as to finely control the opening degree (the lift amount) so as to achieve the function of the expansion valve and finely control the valve opening degree, that is, the flow rate of the refrigerant, for example, at a time of the heating operation.
However, in order to make the electrically operated valve 1′ serve as the bypass valve, it is necessary to minimize the pressure loss. In this case, it is necessary to make a valve bore diameter equal to or more than a piping diameter of the heat pump type cooling and heating cycle. For example, on the assumption that the piping diameter is 10 mm, the valve bore diameter equal to or more than it is necessary.
As a result, since a great toque is required in an actuator for driving, the electrically operated valve is enlarged in size and an electric power consumption becomes large.
On the other hand, in order make the electrically operated valve 1′ serve as the expansion valve, it is necessary to enhance a resolving power of the flow rate control, however, in this case, it takes long time to reach a full open state (a flow path bypass state) from a micro flow rate control state at a time of the heating operation, and an opening gap (a gap between the valve body portion and the valve port) at a time of the small flow rate control becomes very narrow, so that there is a risk that a foreign material or the like is bitten into the gap.
Accordingly, in order to achieve both an improvement of a flow rate control precision and an increase of a controllable flow rate (a reduction of the pressure loss) at a time of the small flow rate, and achieve a reduction of a time from the time of the small flow rate to the maximum opening degree, the following Japanese Official Gazette of Patent No. 4416528 discloses a provision of a pilot type first control valve (a first valve body and a first valve port) for a large flow rate and a second control valve (a second valve body and a second valve port) for a small flow rate, in more detail, a composite valve structured such as to open and close the first valve port having a large bore diameter by the piston type first valve body, open and close the second valve port having a small bore diameter by the needle type second valve body which is an independent body from the first valve body and is provided in the lower portion of the valve shaft, and make the second control valve for the small flow rate serve as the pilot valve of the first control valve for the large flow rate.
In this composite valve, when the lift amount of the valve shaft (the second valve body) is equal to or less than a predetermined amount (when the second control valve opening degree is equal to or less than a predetermined value), there is established a small flow rate control state in which the first valve body closes the first valve port, and the second control valve opening degree for the small flow rate is controlled by the second valve body. At this time, the refrigerant at an amount corresponding to the lift amount (the second control valve opening degree) of the second valve body flows to the inflow port→the first valve chamber→the gap of the sliding surface formed between the outer peripheral surface of the first valve body and the wall surface of the first valve chamber→the back pressure chamber→the pilot passage→the second valve chamber→the second valve port→the outflow passage→the outflow port. Further, if the lift amount of the valve shaft (the second valve body) goes beyond the predetermined amount, the amount of the refrigerant flowing out of the back pressure chamber via the second valve port is increased in comparison with the small flow rate control time, the pressure of the back pressure chamber is lowered, and the valve opening force becomes finally larger than the valve closing force acting on the first valve body, whereby the first valve body opens the first valve port, and there is established a large flow rate control state in which the refrigerant flows to the inflow port→the first valve chamber→the first valve port→the outflow port.
As mentioned above, it is possible to achieve both the improvement of the flow rate control precision at a time of the small flow rate and the increase of the controllable flow rate (the reduction of the pressure loss), and the low electric power consumption, by opening and closing the first valve port having the large bore diameter by means of the first valve body, opening and closing the second valve port having the small bore diameter by means of the second valve body, and making the second valve body serve as the pilot valve of the first control valve for the large flow rate.